1. Animals
AP Biology - Chapter 32

2. What is an Animal? Eukaryotic No cell wall Heterotrophic
Bodies held together by collagen, tight junctions desmosomes and gap junctions (proteins)
Heterotrophic
Ingest then digest
All reproduce sexually
some also reproduce asexually

3. Reproduction and Development
Sexual
Diploid stage is dominant
Small sperm fertilizes larger, nonmotile egg.
This makes a diploid zygote

4. Development Zygote undergoes cleavage
Succession of mitotic cell divisions without cell growth in between the divisions.

5. Development Cleavage leads to the formation of a blastula
Hollow ball of cells

6. Frog Blastula and Future Embryonic Tissue Layers

7. Development
The blastula then turns itself “inside out” to form the gastrula
This process is known as gastrulation; frog1; frog 2; frog 3
This process produces the layers of embryonic tissues that will develop into the adult body parts.

8. Gastrulation
Bastocoel – cavity in the blastula that provides space for gastrulation to occur
Archenteron – the future gut cavity; forms during gastrulation
Blastocoel gets smaller as gastrulation takes place.

9. Larvae Some animals develop directly into adults
Other animals must pass through a larval stage
Sexually immature form of an animal that is morphologically distinct from the adult
Eats different food
Different habitat
Tadpole > frog
metamorphosis

10. History of Animals Diversification began more than 1 billion years ago
Common ancestor of the animals may have resembled modern choanoflagellates
Protist that is the closest living relative of animals
Colonial, flagellated protist

11. One hypothesis…
…for origin of animals from flagellated protist..(the arrows represent evolutionary time).

12. Animal Body Plans Features of Body Plans
Symmetry
Tissues
Body Cavities
Protostome vs. Deuterostome development
Body plans allow us to talk about levels of complexity

13. Symmetry
Asymmetry – no symmetry - sponge

14. Symmetry Radial symmetry “Flower pot” Top and bottom (oral and aboral)
No left/right; no head/tail

15. Symmetry Bilateral Symmetry
Dorsal / ventral
Left / right
Anterior / posterior
Sensory equipment concentrated at head end and central nervous system
Cephalization; more efficient way to encounter the world when you are moving through it (rather than having the world drift around you)

16. Tissues
Tissue
Collection of cells that are similar in structure and work together to carry out a common function

17. Tissues Some animals lack tissues Sponges
really just an aggregate of individual cells
Individual cells function nearly independently, though not entirely independent

18. Tissues
In animals with tissues the embryo becomes layered through gastrulation
Embryonic Layers = germ layers
These will form the various organs/tissues of the body
The germ layers include
Ectoderm
Endoderm
Mesoderm

19. Embryonic Tissue (Germ) Layers
Diploblastic
An animal that has only two germ layers
Ectoderm, Endoderm
Jellyfish/coral (phylum cnidaria)
Triploblastic
An animal that has three germ layers
Ectoderm, Endoderm, and Mesoderm
all animals higher than the jellyfish/coral

20. Embryonic Tissue Layers – Germ Layers
Ectoderm
Covers the surface of the embryo
Gives rise to
Outer covering
CNS
Endoderm
Innermost germ layer
Lines the gut
Gives rise to organs like liver, lungs
Mesoderm
Between the ecto and endoerm
Forms muscles and most organs that lie between the digestive tract and outer covering

21. Body Cavities Body cavity COELOM
Fluid-filled space that separates the digestive tract from the outer body wall
The space in which you find all the body’s internal organs
Functions
Fluid cushions suspended organs
Hydrostatic skeleton in soft bodied animals (worms)
Organs move independently of outer surface
Some animals lack a coelom totally, some have a true coelom and some have a “sort of” coelom.

22. Body Cavities Acoelomate Animals Lack a body cavity
They HAVE a gut space for food, but NOT a hollow space that contains the organs
“solid body”
flatworms

23. Body Cavities Pseodocoelomate Animals
Have a space that contains the body organs, but it is not lined totally with mesoderm
Thus it is not defined as a “true” coelom
Round worms
Hydrostatic skeleton

24. Body Cavities Coelomate animals Possess a True Coelom
Cavity that is completely lined with mesoderm
Contains fluid and the body organs
Segmented worms and higher

25. Protostome vs. Deuterostome Development
Distinguished by 3 features
Cleavage pattern
Coelom formation
Fate of the blastopore

26. Protostome vs. Deuterostome
Protosome
Spiral cleavage
Determinate cleavage
Each embryonic cell’s fate is rigidly cast
Deuterostome
Radial cleavage
Indeterminate cleavage
If separated, each embryonic cell retains the ability to become a new embryo
Makes identical twins possible
Makes embryonic stem cells of high interest to researchers

27. Protostome vs. Deuterostome
Coelom formation
See diagram

28. Protstome vs. Deuterostome
Fate of Blastopore
Blastopore
Indentation that leads to the formation of the archenteron during gastrulation
After gastrulation a second opening forms at the opposite end of the gastrula
Ultimately the blastopore and the second opening become the two openings of the digestive tube
Mouth / anus

29. Protostome vs. Deuterostome
In a protostome
The blastopore becomes the MOUTH
Segmented worms, mollucscs and arthropods

30. Protostome vs. Deuterostome
In a deuterostome
The blastopore becomes the ANUS
Echinoderms and chordates

32. Animal Phylogenetic Tree
About 35 animal phyla are recognized
Relationships between them are debated
Points in agreement:
All animals share a common ancestor
Sponges are basal animals (and the phylum is paraphyletic)
Eumetazoa is a group of animals with true tissues
The cnidarians are basal
Most animal phyla belong to the clade bilateralia
Vertebrate and some others belong to the clade deuterostomia

35. Embryonic Development

36. Embryonic Development

37. Embryonic Development

38. Choanoflagellate

39. Animal Origins

41. Symmetry